Cystic fibrosis, an autosomally recessive disease, has long been recognized as a disease of glandular secretion. Affected tissues secrete less water resulting in thick mucus congestion of the lungs, airway passages, pancreas and intestine. The collective works of several laboratories have shown the disease to be a defect in the secretion of chloride ions from epithelial cells. More specifically, it has been shown that cystic fibrosis is a diseae of chloride channel regulation. Normally, this channel is opened in response to the second messenger cyclic AMP and calcium. CF patients show failures to secrete chloride in response to cyclic AMP and in some tissues calcium mediated secretagogues. For the past several years our laboratories have been investigating the mediation of intracellular calcium through the identification of high affinity calcium-binding proteins. Recently a family of calcium/phospholipid-binding proteins had been identified yet specific cellular function has only been implied. We propose to use immunohistochemical techniques to localize thee "calcimedins" in transporting epithelia. In addition subcellular apical and basolateral membrane fractions will be analyzed for calcimedin content, calcium- dependent calcimedin-binding and calcimedin-binding proteins. Regulations of the epithelial chloride channel by the calcimedins will be through reconstitution studies in artificial bilayers, whole-cell patch-clamp and inside-out membrane patches. Efforts will be made to reconstitute tracheal, small intestine and rectal gland chloride channels in order to delineate the regulatory elements which may include one of the calcimedins. One means of pharmacologically treating cystic fibrosis would be to activate a calcium mediator causing he channel to open and potentially ameliorate the chronic condition.